Modem automobile body shapes are distinguished by relatively large window areas. Because of strong sunlight, the large window areas result in considerable heat generation in the interior of the vehicle and, in connection with vehicles with air conditioning, this major heat generation results in a considerable use of energy in order to counteract the heating effects on the vehicle.
For this reason, motor vehicles are increasingly equipped with windup window shades. A rear window windup shade is known from DE 36 12 165 A1, which has a windup shaft which is rotatably seated in a base. The base is located on or underneath the rear window shelf. The window shade web of the rear window windup shade is pulled out from the rear window shelf in the direction toward the rear edge of the roof. The windup shaft, which is rotatably seated in the base and is biased by a spring drive in the windup direction, is used for storing the unused part of the window shade web. A traction rail is fastened on the edge of the window shade web remote from the windup shaft. With the aid of second pivot levers, the traction rail is transferred from a position in which it directly adjoins the windup roller into a position in which the window shade web covers nearly the entire window. For this purpose the pivot levers are essentially rigid in the direction perpendicular to that plane in which they move in the course of the retraction and extension of the windup shade.
Only two settings for light penetration through the rear window are possible with the known blind. In one state light can enter unhampered through the rear window, because the windup shade is completely wound on the windup roller, while in the other state a reduction occurs in accordance with the permeability to light of the windup shade web.
It is furthermore known to attach two guide rails laterally next to the window, in which the end of the traction rod of the window shade web is guided. The length of the traction rod is adjustable in order to be able to accommodate various window widths. Actuation takes place by means of the thrust members running in the guide rails.
Only two states are possible here, too, namely the unhampered entry of light or reduction in accordance with the reduction effects of the windup shade web.